1. Field of the Invention
The present invention relates to an apparatus for installing, for example, cable or wiring in an electrical conduit, and more particularly, the present invention relates to a device for first sending a pull line under pneumatic pressure through an electrical conduit, and thereafter retrieving the same pull line with a desired cable or heavier pull line attached thereto.
2. General Background and Prior Art
The provision of electrical circuits in residential, commercial and industrial structures conventionally involves the initial placement of junction boxes and interconnecting conduit which can be either rigid or flexible. Thereafter, links of electrical conducting wire are installed between the junction boxes through each connecting link of conduit. When this task is completed, the exposed wire ends of the electrical cable are connected to switches, appliances and the like in a desired manner. A problem arises in the installation of rigid electrical cable, usually copper, through the bending, turning conduit between junction boxes at the conduit ends. For the most part, conduit is relatively small allowing only a minor amount of space after the cable is installed.
The present practice in the industry is the utilization of a vehicle with a line attached, which carrier is propelled through the conduit by means of pneumatic pressure applied by using a cylinder of compressed gas or the like to one end inlet of the conduit. The vehicle, which can be of foam rubber, for example, exits at the opposite end portion of the conduit through which cable will be installed. Generally, the carrier will have an attached line which will be hooked to a desired heavier pull line or directly to the electrical wire or cable itself, and then pulled by hand back through the conduit to make the necessary installation. This involves in many instances a vast waste of materials as each line is discarded after a single use.
Several devices have been patented which attempt to solve the problem of installing pull lines in electrical conduit. Examples of these prior art devices which have been patented are listed in the following table.
______________________________________ PRIOR ART PATENTS ______________________________________ U.S. PAT. NO. INVENTOR(S) ISSUE DATE ______________________________________ 1,827,239 C. E. Kelley 10/13/31 3,119,600 K. D. Bitter 1/28/64 3,179,375 J. C. Hamrick 4/20/65 3,301,531 R. J. Corsiglia 1/31/67 3,689,031 Ruddick et al. 9/5/72 3,793,732 J. C. Hamrick 2/26/74 3,837,624 T. G. Dandurand 9/24/74 ______________________________________
The devices which have been patented generally require the use of a new piece of feed line to be threaded through the conduit on each installation. This is both costly and wasteful.
Several of the prior devices do not have a means for rewinding the string, thus the string is merely pulled through and discarded after each use. Other devices are extremely complex and therefore costly, utilizing "vehicles" which travel through the conduit that are complex and expensive to manufacture. Some devices require the use of electricity, which can be a problem where electrical power is not available as is often the case in the preliminary stages of construction of a particular structure.